The present invention relates to a process for producing a foamed rubber having a light weight (namely, a low density), a high stress and a low compression set. The word xe2x80x9chigh stressxe2x80x9d means that a 100% tensile stress is high for a density of the foamed rubber.
Since an ethylene-xcex1-olefin copolymer rubber has superior physical properties such as weather resistance and ozone resistance, a foamed rubber obtained by foaming said rubber has been extensively used for applications such as car parts, particularly as sealing materials of a door and a luggage room of a car. From a viewpoint of valance between sealing performance and easy shutting of a door and a luggage room, almost all foamed rubbers applied therefor have been those having a density of 0.5 to 0.7 and a 100% tensile stress of not less than 0.9 MPa.
From a viewpoint of improving fuel cost saving particularly in the application for car parts, there has been demanded a foamed rubber which has a lightest weight possible as well as essential mechanical properties. However, if an expansion ratio in a conventional foamed rubber is increased in order to decrease the density only, sealing performance of the resulting foamed rubber is decreased with decrease of a 100% tensile stress, and as a result the above-mentioned demand cannot be satisfied.
It is an object of the present invention to provide a process for producing a foamed rubber having a lightweight, a high stress and a low compression set.
The inventor of the present invention has undertaken extensive studies to develop a process for producing a foamed rubber having a lightweight, a high stress and a low compression set. As a result, there has been found a surprising fact that a foamed rubber obtained by foaming a rubber composition comprising an ethylene-xcex1-olefin copolymer rubber, mica and a foaming agent has a higher expansion ratio, namely, a lighter weight than that obtained by foaming a conventional ethylene-xcex1-olefin copolymer rubber composition. Thereby, the present invention has been obtained.
The present invention provides a process for producing a foamed rubber comprising a step of foaming a rubber composition, which composition comprises:
(A) 100 parts by weight of an ethylene-xcex1-olefin copolymer rubber,
(B) 10 to 100 parts by weight of mica, and
(C) 2 to 10 parts by weight of a foaming agent.